A new study by The National Institute of Drug Abuse researched the tolerance of THC in adult males. The results show that the psychotropic effects (i.e. getting high) get less with continued use. Meaning that opponents who say the drug is not safe for use by drivers, no longer have a leg to stand on.
The research was conducted on thirteen adult male smokers who had to stay in a lab setting during the study. They were given a THC pill which increased in dosage each day until they reached the maximum dose of 120 mg (or the equivalent to three joints of medical cannabis). Each participant had smoked at least 1000 times. Of the thirteen men, two dropped out. O ne for personal reasons and another to psychological reactions to the dosage.
The result was that the participants felt only half as high on day five as they did on day one. This means that the amount of THC in their blood stream remained the same but the high effect decreased.
Those who favor legalized marijuana fear that opponents will twist the research to mean that the use of marijuana leads to physical dependence.